Miniaturized integrated sensor platform

ABSTRACT

A miniaturized integrated sensor ( 50 ) useful for indicating the presence of a sample analyte is disclosed. The sensor ( 50 ) has a platform ( 52 ) with an upper surface ( 53 ) and a detector ( 62 ), light source ( 60 ), waveguide ( 58 ), and reflective fixtures ( 60,62 ) embedded in the platform ( 52 ). The light source ( 60 ) is preferably a light emitting diode and sits in a cup-shaped dimple ( 68 ) that directs light from the light source ( 60 ) toward one of the reflective fixtures ( 64 ) to uniformly distribute light across the waveguide ( 58 ). The waveguide ( 58 ) is coupled to an upper surface ( 53 ) of the sensor platform ( 52 ) and is coated with a thin film of indicator chemistry ( 70 ) which interacts with the sample analyte to produce optic signal changes that are measurable by the detector ( 62 ). A lead frame ( 51 ) in the platform ( 52 ) has pins ( 54, 55, 56 ) which provide the interface to the outside world. In one embodiment, sensor package ( 100 ) has a unique shape that requires a predetermined insertion and removal into an instrument harness or other similar application.

BACKGROUND OF THE INVENTION

[0001] Without limiting the scope of the invention, its background isdescribed in connection with a (bio)chemical sensor wherein a thin film,fiber or other article is chemically treated with a substance known tointeract in the presence of a second substance so as to produce areaction which can be detected and quantified by analytical methods.

[0002] (Bio)chemical sensor systems have been developed and used in thefields of chemical, biochemical, biological or biomedical analysis,process control, pollution detection and control and other areas. Atypical application involves the chemical coating of a thin film, cableor other article followed by excitation and measurement in the presenceof the particular sample of interest. Recent advances in miniaturizedsensor technology have resulted in three popular configurations:fluorescence-based, surface plasmon resonance, and light transmissionsensors.

[0003] A known prior art sensor system is the fluorescence-based fiberoptic oxygen cable sensor which uses a single high brightness LightEmitting Diode (LED)to produce an excitation signal that catalyzes theemission properties of the fluorescence coating material. The excitationsignal is first guided through a filter and then through the cable,which is coated, unclad, and mounted in a gas flow cell. Light escapingthe cell excites the coated dye on the cable which, in turn, emits acertain intensity of light related to the concentration of the oxygensample. The emitted light is then directed through a second filter andto a light detector via a collecting lens. The output of the detector isamplified and read out on an instrument.

[0004] Another known prior art sensor system uses a multi-pinhermetically sealed package that encloses all of the light filtering,light guiding and light detection components within. The package can beinserted into a socket or slot of a computer or other system processorcreating an interface between the sensor and the processor via the pins.Due to the number of pins, however, replacing, removing or inserting thechip may be difficult or require special tools.

[0005] Prior art sensor systems have limited use in most practical fieldapplications. The signal generator, LED, lens, filter, detector,amplifier and other components are bulky, require significant amounts ofwork space and cannot be easily transported to the sample site. Thecosts of manufacturing and maintaining such systems are high prohibitinghigh volume manufacturing.

[0006] Moreover, prior art sensors are not designed for low costdisposable applications wherein the sensor can be disposed after servingits useful life. A cost effective sensor having an onboard power cellhas not been contemplated and, as such, prior art sensor packagesrequire an interface to an external power supply or other source ofoperating power.

[0007] Another limitation of the prior art sensors the number and typesof components used which in many instances are custom made based on theparticular application. System maintenance is high and requiresspecialized knowledge.

[0008] Yet another limitation of the prior art sensors is systemintegration with equipment such as a personal computers, hand heldinstruments or other signal processors used to measure and quantifysample data. A dedicated bus or interface between the sensor and theprocessor is required increasing the number of signal paths between thesensors detector and the processor.

SUMMARY OF THE INVENTION

[0009] Prior art sensors can not be used in most disposable and fielduse applications. The recent availability of low cost high intensitylight sources and miniaturized detector components, however, permits thedesign of a more compact and miniaturized sensor platform. Aminiaturized sensor would provide many advantages over the bulkier priorart sensor systems which are better suited for laboratory and researchapplications.

[0010] As such, it is a primary object of the present invention toprovide a miniaturized integrated sensor capable of use in opticallyguided sensing applications. The sensor package of the present inventionintegrates a light source, detector means, light guide optics and asimplified system interface into a compact miniaturized package. In oneembodiment, the package incorporates an onboard power source, such as alithium cell battery of the type readily available in industry, givingthe sensor a useful lifetime equal to that of the power source. Thus, afully operable sensor is disclosed that can be easily replaced anddiscarded after use.

[0011] Another object of the present invention is to provide aminiaturized sensor with a simplified interface to external systems suchas computers, signal processors, and other similar processors whichperform analytical processing of the output from the sensor's lightdetector. In one embodiment, the sensor package has a three-pin leadframe extending from the platform with signal conduits to power, groundand the detector output. In a second embodiment, a two-pin version isprovided wherein the onboard power source eliminates the need for athird signal interface.

[0012] Yet another object of the present invention is to provide asensor with a uniquely shaped package which fits securely into anopening or mounting harness in a hand held instrument, computer or othersimilar fixture. In one embodiment, the sensor housing is shaped andsized to fit a fixture in a hand held application specific instrumentwhich uses the sample data from the sensor to perform further signalprocessing and analytical functions. Surface contacts on the sensorwalls provide the interface with the instrument. Since the device isuniquely shaped it fits into the mounting harness about a predeterminedposition allowing simple insertion and removal.

[0013] Disclosed in one embodiment of the invention, is an integratedsensor for detecting the presence of one or more specific materialsamples of interest having a platform to which a light source, detector,waveguide and reflective pyramidal structures are affixed to form aminiaturized fully integrated sensor package. A three-pin lead frameextends from the sensor package providing the interface between thesensor and an external processor. In another embodiment, surfacecontacts provide the same function. Power can be external or providedinternally by a self contained battery cell which is coupled to theplatform and the various active components of the sensor. In yet anotherembodiment, the package is uniquely shaped and sized requiring a uniqueplacement within a mounting harness in a computer, hand held instrument,wall mount harness or other similar fixture.

[0014] For a more complete understanding of the present invention,including its features and advantages, reference is now made to thefollowing detailed description, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the drawings:

[0016]FIG. 1 depicts a prior art sensor platform;

[0017]FIG. 2 is a top side view of a miniaturized integrated sensorpackage according to one embodiment of the invention;

[0018]FIG. 3 is a cross sectional view of the sensor package of FIG. 2;

[0019]FIG. 4 is an alternative embodiment of a sensor package accordingto the invention;

[0020]FIG. 5 illustrates the internal arrangement of sensor componentsfor the sensor package of FIG. 4;

[0021]FIG. 6 is a side profile view of an miniaturized sensor packagehaving an internal power source according to the invention; and

[0022]FIG. 7 shows use of a miniaturized integrated sensor in and easyto install and remove instrument application.

[0023] Corresponding numerals and symbols in the different figures referto corresponding parts unless otherwise indicated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] Referring now to FIG. 1, a prior art sensor is shown and denotedgenerally as 10. Sensor 10 is used in biochemical sensing application todetect the presence of a given sample gas, liquid or compound bydetecting optical changes produced by the molecular interaction betweena thin layer of biochemistry coat and the particular sample of interest.The chemistry is chosen for its interactive properties in the presenceof the sample and, as such, the sensor 10 has widespread applicationdepending on the particular chemistry/sample combination of interest.Suitable combinations chemistry/sample combinations includechloride/oxygen, hydroxypyreneprisulphonic acid/carbon dioxide sample,octadecyl fluorescein/nitrate and acetic acid/alcohols. Othercombinations are numerous and well known in the art.

[0025] As illustrated in FIG. 1, sensor 10 has a platform 12 to whichthe various sensor components are affixed. The platform 12 is made of asuitable substrate material and in some embodiments has a lightabsorbent quality that acts to eliminate scattered light. Coupled to thebottom surface 14 of the platform 12 are pins 16 which provide thesignal interface between the sensor 10 and other remote processingsystems (not shown). In this way, the sensor 10 receives power andcommunicates with the outside world.

[0026] Affixed to the upper surface 18 of the platform 12 are thevarious sensor components including light source 20, waveguides 22 and24, and detectors 26 and 28. The specific device embodiments of thesecomponents vary depending on application although for miniaturizedsensor some devices are preferred. For example, it is common for lightsource 20 to be a single high brightness light emitting diode (LED) ofthe type commonly available in industry. A light-to-voltage sensor, suchas the TSL250, can be a suitable device component for detectors 26 and28, although other detector component may also be used.

[0027] Waveguide 24 is chemically coated depending on the sample ofinterest and either molded as part of the sensor package or attachedlater depending on application and specific chemistry. Waveguide 22 isuntreated or partially untreated providing a base point for signalreferencing. In operation, the light source 20 generates an outputsignal with a wavelength characteristic that interacts with the coatingmaterial. The output signal from light source 20 is first directed bycast 30 into each waveguide 22, 24, which are made of a lighttransmissive material, where it reflects internally off thecorresponding waveguide surface and towards the detectors 26, 28.

[0028] When a given sample, i.e., oxygen, carbon dioxide, nitrate,alcohols and others, comes in contact with the waveguide 24 surface, thechemical coat thereon changes its optical properties so that the totallight incident on the detector 28 is measurably altered. As known andappreciated by those skilled in the art, the excitation signal fromlight source 20 interacts with the chemical coat which, in turn,interacts with the sample of interest to alter the total lighttransmitted through the waveguide 24 related to the sampleconcentration. A portion of this transmitted light is gathered bysensing surface of the detectors 28 and amplified to create a voltageswing indicative of the sample's presence.

[0029] The output signals from the detectors 26 and 28 can be comparedto provide a differential output. This output is accessed throughinterface 26 and analyzed by a remote processing system whereinanalytical derivation is performed and meaningful information regardingthe sample is obtained.

[0030]FIG. 1 illustrates a prior art sensor system having a lighttransmission device configurations wherein a light wavelength isdirected across one or more treated waveguide members (26,28). It shouldbe understood, however, that other platform types and arrangements maybe employed or exist in the prior art and, as such, it is intended thatprinciples and advantages of the present invention apply withoutlimitation to all such configurations. For example, the presentinvention may have application in the fields of surface plasmonresonance and fluorescence based sensors. In this regard, reference ismade to the following wherein the operating and functional aspects ofsuch devices are discussed: Ralph C. Jorgensen, Chuck Jung, Sinclair S.Yee, and Lloyd W. Burgess, Multi-wavelength surface plasmon resonance asan optical sensor for characterizing the complex refractive indices ofchemical samples, Sensors and Actuators B, 13-14, pp. 721-722, 1993; B.D. McCraith, G. O'Keeffe, C. McDonoagh, and A. K. McEvoy, LED basedfiber optic oxygen sensor using sof-gel coating, Electronic Letters,Vol. 30, No. 11, pp. 888-889, May 26, 1994.

[0031] Turning now to FIGS. 2 and 3, the advantages of the presentinvention over the prior art sensor platforms are illustrated and madeapparent to those skilled in the art. FIGS. 2 and 3 depict analternative sensor package for a miniaturized (bio)chemical sensorhaving a reduced pin count and significant size advantages over theprior art. Specifically, FIG. 2 shows a top side view of a miniaturizedsensor 50 in accordance with one embodiment of the invention. FIG. 3 isa cross sectional view of sensor 50 taken along line X.

[0032] Sensor 50 has a platform 52 which forms a substantiallyrectangular box shaped housing for the various sensor components. Theplatform 52 can be made of a plastic, hard resin material, epoxysubstance or similar substrate material and may be molded or pre-shapedfrom a cast die providing a low cost and easy to manufacture device.

[0033] A lead frame 51 has pins 54, 55 and 56 which extends outward fromthe platform 52 and provide the interface to the outside world. In oneembodiment, pins 54, 55 and 56 correspond to ground, power and output,respectively.

[0034] Coupled to the sensor platform 52 is waveguide 58 which extendsalong a substantial portion of upper surface 53 of platform 52.Waveguide 58 is made of a light transmissive material such as glass, aceramic substrate, clear plastic or similar material. A light source 60and detector 62 are embedded in the platform 52 substrate about oppositeextremities of the waveguide 58. Triangular shaped reflecting fixtures64 and 66 are coupled to opposite ends of the waveguide 58 and also toupper surface 53 of the platform 58.

[0035] Fixtures 64 and 66 work to direct the light energy from the lightsource 60 to detector 62 via waveguide 58. The placement of fixture 64above light source 60 and fixture 66 above detector 62 helps achieve auniform dispersement of light across the waveguide surface therebyimproving the coupling characteristics of light from the light source 60to the detector 62. It should be understood, however, that othercoupling means may be devised and are within the scope of the presentinvention.

[0036] Light source 60 is centrally configured inside dimple 68 whichforms a substantially cup-shaped reflective bevel underlying lightsource 60 and serves two primary purposes. First, dimple 68 directslight from light source 60 to fixture 64 which in turn reflects anddistributes the light more evenly along the coated surface 70 onwaveguide 58. Second, dimple 68 minimizes the amount of light from thelight source 60 that reaches the detector 62 directly, without havinginteracted with the coated surface 70.

[0037] Likewise, the detector 62 sits inside dimple 69. In the preferredembodiments, dimples 68 and 69 are stamped in the lead frame 51 duringmanufacture thus limiting the number of separate parts.

[0038] As shown, the detector 62 is centrally placed in an underlyingfashion about reflecting fixture 66 giving the detector 62 a uniformarea of light reception that increases sensitivity to light emissionsfrom coated surface 70.

[0039] Thus, a complete sensor is disclosed having a light source 60,detector 62 and waveguide 58 components among others. The components areoperably coupled to each other in a manner known to those skilled in theart according to the invention. For example, without limiting theinvention, the following circuit diagram demonstrates one possiblearrangement of the components according to the invention:

[0040] In general, the light source 60 is implemented as a seriescombination of a light emitting diode LED and a limiting resistor R. Aphoto diode amplifier chip, such as the Texas Instruments, Inc. TSL250,is a suitable device for this purpose. Power level Vcc and a referenceGND are two inputs of the package lead frame while the detector outputcomprises a third pin. A two-pin embodiment is also envisioned whereinan internal power source, such as a Lithium cell or charged cellcapacitor, is included eliminating the third pin to the sensor 50. Thisconfiguration is illustrated in FIG. 4 wherein power source 74 isembedded in the platform 52 and interfaced to the light source 60 vialead 76 and to the detector 62 via lead 77. Other arrangements may beobtained all within the scope of the invention.

[0041] As illustrated by FIGS. 2, 3 and 4, a primary advantage of sensor50 over prior art devices is its small size, miniaturized dimensions andsmall lead count. The sensor package can be manufactured according toexisting platform standards, such as the TSL250 light-to-voltage opticalsensor of Texas Instruments, Inc. which combines a photo diode/amplifierin a clear plastic three-pin package having an active area ofapproximately 1.0 mm². Other package types and dimensions are alsoenvisioned and within the scope of the present invention.

[0042] In the preferred embodiment, a coated surface 70 on the waveguide58 forms a thin film of an absorbing chemistry chosen for how itinteracts with the sample of interest to produce a detectable signalchange. The properties of chemical coat 70 are well known in the art.For example, in one embodiment an indicator is embedded in a matrix suchas a polymer or a sol-gel and deposited on the waveguide 58. Examples ofsuch indicators and the corresponding sample analyte are listed below:INDICATOR ANALYTE WAVELENGTH Magon Magnesium 520 mn Pyrogallolred-molybdate Total Protein 600 nm Brilliant blue G. (Coomassie blue)Total Protein 595 nm Ferrozine Iron 560 nm Picric acid Creatinine 500 nmArsenazo III Calcium 600 nm Bromcresol Albumin 628 nm

[0043] Turning now to FIG. 5, an alternative package configuration for aminiaturized integrated sensor in accordance with the invention is shownand denoted as 100. The package 100 has surface contacts 105, 107 and109 which extend from three substantially noncoplanar walls of thepackage 100 and form a trapezoidal shaped structure. The shape andarrangement of the package 100 ensure unique insertion of the sensorwithin a mounting harness or other fixture where the sensor is insertedor removed from.

[0044] Contacts 105, 107 and 109 provide conductive pathways to theinternal device electronics and other components as illustrated in theabove circuit diagram and in FIG. 6. The waveguide 58 occupies a portionof at least one surface of the package 100 and has the thin layer ofchemical coating thereon. The waveguide 58 can be integrally molded onthe package or attached separately depending on the chemical coat anddesign.

[0045] A principle advantage of the package 100 is the shape whichrequires unique placement in a predetermined orientation into a mountingharness or similar opening in a hand held application specificinstrument. An application of such a use is illustrated in FIG. 7.Snap-in insertion and removal of the package 100 is facilitated by locks112 which can be placed on a package surface to lock the device inplace.

[0046] The short length of the contacts 105, 107 and 109 makes thepackage 100 ideal for disposable applications since it can be easilyinserted and removed by the user.

[0047] It should be understood, however, that the invention encompassesmore than the trapezoidal shaped housing of FIGS. 5 and 6, and that theinvention may be practiced using a plurality of package configurationsall of which restrict and define the placement of the sensor within amount, harness or instrument panel.

[0048] In FIG. 7, use of the package 100 in a hand held instrument 125is illustrated. The size, weight and construction of instrument 125makes it ideal for field use near the sample of interest. Controls 130give access to various functions and commands depending on theapplication and nature of the instrument 125. For example, theinstrument can be used to detect hazardous substances at a givenlocation or the smoke content in the air. Other uses are alsoenvisioned.

[0049] A screen display 135 provides visual feedback informationconcerning the sample and can be used to view results and other data.

[0050] The instrument harness 140 is provided to secure the sensorpackage 100 within instrument 125. As shown, the harness 140 has beenshaped and sized to accommodate the package 100, although manyconfigurations of the harness 140 are embodied by the invention. Sincethe harness 140 is shaped to fit the sensor package 100, the user isrequired to place the sensor in a predetermined orientation within theharness 140.

[0051] The harness 140 includes three mating contacts 142, 144 and 146which interface with surface contacts 105, 107 and 109 of sensorpackages 100 respectively to provide a communications pathway betweenthe detector 62 and the instrument 125. This establishes the signalspaths for power, reference and the detector output.

[0052] While this invention has been described in reference toillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiments, as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. It is therefore intended that the appended claimsencompass any such modifications or embodiments.

What is claimed is:
 1. An integrated biochemical sensor packagecomprising: a platform; a waveguide having an upper surface affixed tosaid platform, said waveguide having a thin layer of chemical coatingaffixed on said upper surface; and first and second reflective fixturescoupled to opposite extremes of said waveguide and touching saidplatform.
 2. The integrated biochemical sensor package according toclaim 1 further comprising: a lead frame extending from said platform ona place parallel to said thin layer of coating; a first dimpleunderlying said first reflective fixture; a light source embedded insaid first dimple and arranged to emit light outward towards said firstreflective fixture; and a detector means embedded in said platform andunderlying said second reflective fixture.
 3. The integrated biochemicalsensor package according to claim 1 wherein said waveguide is made of alight transmissive material.
 4. The integrated biochemical sensorpackage according to claim 2 wherein said lead frame has three pinsextending outward from said platform.
 5. The integrated biochemicalsensor package according to claim 2 wherein said lead frame has two pinsand further comprising a power source embedded in said platform andhaving a first lead coupled to said light source and a second leadcoupled to said detector.
 6. The integrated biochemical sensor packageaccording to claim 1 wherein said light source is a series combinationof a diode and resistor.
 7. The integrated biochemical sensor packageaccording to claim 2 wherein said detector means is an photo diodeamplifier chip.
 8. The integrated biochemical sensor package accordingto claim 2 wherein said light source is a single high intensity lightemitting diode.
 9. The integrated biochemical sensor package accordingto claim 1 wherein said platform forms a substantially rectangularshaped enclosure for housing various sensor components.
 10. Theintegrated biochemical sensor package according to claim 1 wherein saidplatform has a substantially trapezoidal shape.
 11. The integratedbiochemical sensor package according to claim 1 wherein said waveguideis integrally molded on said platform.
 12. The integrated biochemicalsensor package according to claim 1 further comprising a second dimpleunderlying said second reflective fixture wherein said detector meanssits inside said second dimple.
 13. A miniaturized integratedbiochemical sensor for indicating the presence of a given sample basedcomprising: a sensor platform having a substantially rectangular boxshape form, said platform having a substantially flat upper surface andat least one end; a waveguide coupled to said upper surface of saidplatform, said waveguide having a first end and a second end oppositefrom one another; a first reflective fixture coupled to said first endof said waveguide and touching said upper surface of said platform; asecond reflective fixture coupled to said second end of said waveguideand touching said upper surface of said platform; a light sourceembedded in said platform under said first reflective fixture; and adetector embedded in said platform opposite said light source about saidone end of said platform and underlying said second reflective fixture.14. The miniaturized integrated biochemical sensor of claim 13 whereinsaid light source is a light emitting diode.
 15. The miniaturizedintegrated biochemical sensor of claim 13 further comprising: athree-pin lead frame extending from said one end of said platform; and afirst dimple forming a substantially cup-shaped area on one pin of saidlead frame and surrounding said light source under said first reflectivefixture.
 16. The miniaturized integrated biochemical sensor of claim 13further comprising: a two-pin lead frame extending from said one end ofsaid platform; and a power source embedded in said platform and having afirst lead coupled to said light source and a second lead coupled tosaid detector.
 17. The miniaturized integrated biochemical sensor ofclaim 13 wherein a thin layer of chemical coating is deposited on saidwaveguide.
 18. A sensor package suitable for biochemical sensingapplications comprising: a substantially rectangular device platform; alight transmissive waveguide coupled to an upper surface of saidplatform and a surface with an indicator chemistry coat depositedthereon; first and second reflective fixtures coupled to opposite endsof said waveguide about said platform; a lead frame embedded in saidplatform and having a plurality of pins extending out from one end ofsaid platform, said lead frame having a first dimple underlying saidfirst reflective fixture and a second dimple underlying said secondreflective fixture; a light source sitting in said first dimple undersaid first reflective fixture; and a detector means sitting in saidsecond dimple under said second reflective fixture, said detector meansconfigured about said platform to optically receive light from saidlight source via said first reflective fixture through said waveguideand then through said second reflective fixture.
 19. The sensor packageaccording to claim 19 further including a power source embedded in saidplatform and having a first lead coupled to said light source and asecond lead coupled to said detector means.
 20. A manufacturing methodof forming a miniaturized integrated sensor platform comprising thesteps of: stamping out a substantially rectangular shaped platform froman epoxy material; embedding a lead frame in said platform about oneend; forming first and second dimple members about opposite ends of theportion of said lead frame that exists in said platform; placing a lightsource in said first dimple and a detector in said second dimple;placing a light guide on an upper surface of said platform; and placingfirst and second reflective fixtures at opposite end of said light guideover said first and second dimples of said lead frame.